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Surgery for atrioventricular node reentry tachycardia
Surgery for atrioventricular node reentry tachycardia Results with surgical skeletonization of the atrioventricular node and discrete perinodal cryosurgery Surgical treatment options for interruption of atrioventricular node reentrant tachycardia include (1) skeletonization of the atrioventricular node by dissecting it from most of its atrial inputs and (2) discrete cryosurgery of the perinodal tissues by applying a series of sequential cryolesions to the atrial tissues immediately adjacent to the atrioventricular node. Both these techniques attempt to interrupt one of the dual atrioventricular node conduction pathways while preserving the other. This report describes 17 consecutive patients who underwent surgical treatment, 10 patients with skeletonization of the atrioventricular node and seven patients with discrete perinodal cryosurgery. There were 10 female and seven male patients and their ages ranged from 28 to 56 years (mean 38). Two of the 17 patients had Wolff-Parkinson-White syndrome and their accessory pathways were interrupted before the atrioventricular nodal reentrant tachycardia was ablated. AIl the procedures were performed in a normothermic beating heart while atrioventricular conduction was monitored closely. In the skeletonization technique, the right atrial septum was mobilized and the atrioventricular node exposed anterior to the tendon of the Todaro. The perinodal cryosurgical procedure was also performed through a right atriotomy and a series of sequential 3 mm cryolesions were placed around the borders of the triangle of Koch on the inferior right atrial septum. There were no operative deaths. Two patients who underwent the skeletonization operation had heart block necessitating pacemaker therapy. At postoperative electrophysiologic study, no echoes or atrioventricular nodal reentrant tachycardia were inducible in any of the 17 patients. AU patients have remained free of arrhythmia recurrence and have required no antiarrhythmic therapy after a foUow-up of 5 to 28 months (mean 14). In conclusion, both atrioventricular node skeletonization and perinodal cryosurgery successfully ablate atrioventricular nodal reentrant tachycardia; however, perinodal cryosurgery appears to be safer in avoiding heart block, is more easily performed, and is our procedure of choice for the management of medicaUy refractory atrioventricular nodal reentrant tachycardia. (J THoRAe CARDIOVASC SURG 1992;104:1035-44) Yousuf Mahomed, MDa (by invitation), Robert D. King, MD,a Douglas Zipes, MD b (by invitation), William M. Miles, MDb (by invitation), Lawrence S. Klein, MD b (by invitation), and John W. Brown, MD,a Indianapolis, Ind.
h e first successful surgical interruption of atrioventricular (AV) nodal reentrant tachycardia occurred forFrom the Departments of Surgery" and Medicine," Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Ind. Read at the Seventy-first Annual Meeting of The American Association for Thoracic Surgery, Washington, D.C., May 6-8, 1991. Address for reprints: Yousuf Mahomed, MD, Indiana University School of Medicine, Department of Surgery, 545 Barnhill Dr., Emerson Hall 212, Indianapolis, IN 46202.
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tuitously after a failed attempt at surgical ablation of the AV node in a patient with incessant AV nodal reentrant tachycardia. I Ross and associates/ subsequently demonstrated the ability to cure AV nodal reentrant tachycardia by surgical dissection with a high success rate and while preserving AV conduction. The operation was based on intraoperative mapping of the retrograde limb of the reentrant circuit during AV nodal reentrant tachycardia. Cox and colleagues- 4 presented a technique in which cryosurgery is used to modify the perinodal tissues along the perimeter of the triangle of Koch with excellent
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Table I. Preoperative electrophysiologic characteristics
Patient No. I
2 3 4 5 6 7 8 9 10
Discontinuous AVN curve
AVNRT cycle length (msec)
+ + +
335 300 420 300 255 350 270 350 320 290 275 420 340 370 300 200 300 323
+ + + + +
II
12 13 14 15 16 17 Mean value
+ + + +11 -6
Shortest VA interval
10 -20 75 0 -10 0 35 0 0 45 -10
85 45 -15 -20 25 40 16.75
Preop. incremental increase in retrograde conduction (msec)
60 40 Fixed
40 20 50 30 10
20 Fixed
20 Fixed
N/A
Fixed
40 60 50
AVN, AV node; AVNRT, AV node reentrant tachycardia; N/A, not applicable.
results, Cryosurgery was chosen because of its unique ability to obtund electrical activity before causing cell death. Recently, Guiraudon and coworkers' presented a dissection technique, which is an anatomically guided "skeletonization" of the AV node from its atrial input, resulting in successful cure of the tachycardia while preserving A V conduction. The purpose of this study is to report our experience with both the A V node skeletonization procedure and the discrete perinodal cryosurgical procedure in 17 consecutive patients with medically refractory A V nodal reentrant tachycardia. Methods Preoperative electrophysiologic study. All 17 patients who underwent surgical treatment for AV nodal reentrant tachycardia had electrophysiologic studies performed preoperatively after informed written consent was obtained. Preoperative electrophysiologic testing was done with the patient in the drug-free, nonsedated, postabsorptive state. Standard 6F multipolar electrode catheters, placed in the high right atrium, in the His bundle region, in the right ventricular apex, and in the coronary sinus for selected patients, were used. In addition to the intracardiac electrocardiograms, surface electrocardiographic leads I, II, III, and VI were recorded simultaneously (PPG VR-16) at paper speeds of 50 to ISO rum/sec. The extrastimulus technique was used to measure the AV nodal effective refractory period (ERP) at 400, 500, 600, and if necessary 700 msec pacing cycle lengths, by means of a stepwise 10 msec decrease in SI and S2. In addition, AV function and ventriculoatrial (VA) function were measured at decreasing SI intervals to the point at which 1:1 conduction failed. Tachycar-
dia was induced by introducing single and double atrial or ventricular extrastimuli. Isoproterenol was used to facilitate tachycardia induction if needed (Table I). Diagnosis of AV nodal reentrant tachycardia. The diagnosis of AV nodal reentrant tachycardia was based on initiation of the tachycardia dependent on a critical delay in the conduction time between the atrium and His bundle (AH interval) and a normal retrograde activation pattern during tachycardia with the earliest activation recorded at the His bundle catheter and termination of the tachycardia by AV nodal block. Criteria that were considered useful, but not mandatory, for the diagnosis of AV nodal reentrant tachycardia included (I) the presence of discontinuous AV nodal conduction curves in response to atrial extrastimuli and (2) a shortest VA interval less than 60 msec; accessory AV connections were excluded in all patients." Intraoperative electrophysiologic study. Intraoperative electrophysiologic studies were obtained with quadripolar, epicardial plaque electrodes sutured to the epicardial surfaces of the right atrium and the right ventricle. These plaque electrodes served both for pacing and for recording atrial and ventricular electrograms. Stimulation studies were undertaken to eliminate the coexistence of concealed. accessory AV conduction and to confirm the presence of AV nodal reentrant tachycardia. Mapping was not necessary to perform either the skeletonization procedure or the discrete perinodal cryosurgical procedure, since both of these methods are anatomically guided. After a right atriotomy was done, a hand-held mapping probe (interelectrode distance 1.5 mm) was used to identify and localize the His bundle. During both the surgical skeletonization procedure and the discrete perinodal cryosurgical procedure, atrial pacing was instituted at a constant cycle length and AV conduction was closely monitored on a beat-to-beat basis with an oscilloscope. After completion of both the skeletonization and perinodal cryosurgical procedure, but before separation from cardiopul-
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monary bypass, a postintervention electrophysiologic study was undertaken in which incremental atrial and ventricular pacing and programmed atrial and ventricular stimulation were used to assess AV conduction and to attempt to induce echo beats or AV nodal reentrant tachycardia. Postoperative electrophysiologic study. Postoperative electrophysiologicstudies were performed 6.5 days (mean) after the operation (range 5 to 8 days) with two pairs of atrial and one pair of right ventricular temporary epicardial pacemaker electrodes placed during the operation. Measurements were recorded in a similar fashion as in the preoperative studies. Surgical technique. The heart was exposed through a standard median sternotomy incision (n = 15) or through a bilateral submammary incision (n = 2) when the latter was requested for cosmetic reasons. Quadripolar epicardial plaque electrodes were sutured to the right atrium and the right ventricle. With the use of incremental pacing and extrastimulus testing, as previouslynoted, the AV nodal reentrant tachycardia was induced and terminated and a ring map of the AV groove was performed to exclude a concealed accessory pathway. Normothermic cardiopulmonary bypass was begun with aortic and bicaval cannulation. The venous cannulas were placed through juxtacaval pursestring sutures so as to gain maximal exposure to the right atrial chamber. Both the superior and inferior venae cavae were snared with tapes. The heart was then electrically fibrillated and a right atriotomy was performed. In the skeletonization procedure, the right atriotomy was placed along the periannular region of the exposed tricuspid anulus in the anteroseptal region. With the cryosurgical technique, a lateral atriotomy was performed. The atrial septum was then gently inspected and probed to exclude the presence of an atrial septal defect or a patent foramen ovale; if such was present, it was closed. The heart was then defibrillated and the remainder of the procedure was performed on a normothermic beating heart. The skeletonization operation. A V node skeletonization was guided by the following anatomic landmarks: the atrial membranous septum, the posterosuperior process of the left ventricle, the tendon of Todaro, and the os of the coronary sinus. The technique involvedthree separate steps: (I) an anteroseptal epicardial dissection, (2) a posteroseptal epicardial dissection, and (3) endocardial exposure of the intermediate AV node by dissection of the lower right atrial septum. The epicardial anteroseptal dissection was performed by mobilizing the AV fat pad in the right coronary fossa and exposingthe tricuspid valve anulus. The posteroseptal epicardial dissection was then performed by mobilizing the right ventricular and right atrial-left ventricular fat pad and exposing the AV junction. The dissection was extended well into the posteroseptal region, exposing the inferomedial right atrial wall and the posterosuperior process of the left ventriclel? (Figs. I and 2). Normothermic cardiopulmonary bypass was instituted after completion of the epicardial dissection, and skeletonization of the intermediate AV node was then performed endocardially. The periannular right atriotomy was extended to the atrial membranous septum. This incision was carefully extended endocardially along the septal portion of the tricuspid anulus to terminate at the point of dissection of the previously exposed posteroseptal region. The septal atrial wall was carefully mobilized to expose the intermediate AV node, which was identifiable by pale yellow fibers. The tendon of Todaro constituted the
A V nodal reentrant tachycardia
10 3 7
Fig. 1. Surgical approach for anteroseptal AV fat pad dissection. The right AV fat pad has been dissected in the right coronary fossa exposing the white fibrous AV ring of the tricuspid anulus. RA, Right atrium; RV, right ventricle; AV, atrioventricular. posterior limits of dissection and the os of the coronary sinus the inferior limits of dissection. Surgical skeletonization of the AV node interrupted the superficial and posterior atrial inputs ofthe AV node leaving only the deep inputs intact'" (Figs. 3 and 4). The discrete perinodal cryosurgical operation. The anatomic landmarks guiding the perinodal cryosurgical procedure were the His bundle and the triangle of Koch. The triangle of Koch is bounded by the tendon of Todaro, the anterior edge of the coronary sinus ostium, and the anulus of the septal leaflet of the tricuspid valve (Fig. 5). The cryosurgical procedure was designed to alter the perinodal tissues of the AV node by creating a series of cryolesions along the borders of Koch's triangle. After institution of normothermic cardiopulmonary bypass, a right atriotomy was performed. The His bundle was identified with a hand-held probe. The heart was atrially paced and AV conduction was monitored very closely. A dry operative field was obtained by placement of flexible intracardiac sump catheters in the os of the coronary sinus and through the tricuspid valve orifice to aspirate blood return from these areas. A 3 mm diameter cryoprobe (Frigitronics, Inc., Shelton, Conn.) was used to create a series of cryolesions along the perimeter of Koch's triangle. The cryoprobe was cooled to -60 0 C and held at each position for 2 minutes to assure cell death.
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Fig. 2. Surgical approach for posteroseptal AV fat pad dissection. The right ventricular and right atrial-left ventricular AV fat pad has been dissected exposing the white (tricuspid anulus) and the posterosuperior process of the left ventricle.
The series of overlapping cryolesions were created beginning inferiorly at the edge of the coronary sinus os and progressing cephalad along the tendon of Todaro, then across the tricuspid valve anulus from the coronary sinus os inferiorly to the His bundle region superiorly, and finally along the coronary sinus os (Fig. 6). A total of nine cryolesions were usually necessary to completely cryoablate the perimeter of the triangle of Koch. Rarely, additional cryolesions were placed inside the triangle to cryoablate as much atrial tissue as possible while preserving AV conduction." If AV conduction prolonged and heart block occurred during cryothermic exposure, cooling was immediately stopped and the cryoprobe flushed with warm saline to facilitate its removal; the cryolesion itself was then further gently irrigated with the warm saline. AV conduction usually returned within 30 to 60 seconds and the prolonged AV interval returned to baseline. Lengthening of the AV interval and transient heart block was most likely to occur during application of the cryoprobe along the tricuspid valve anulus near the His bundle. If lengthening of the AV interval and heart block did occur, cryothermia was immediately terminated. After resumption of A V conduction and return of the AV interval to baseline, the cryoprobe was reapplied, moving it more closely toward the anulus for 2 minutes at each site. A full 2 minutes of cryothermic exposure was necessary at each location to assure cell death while avoiding heart block. The unique ability of cryothermia to obtund cellular activity before causing cell death permitted this approach.f- II Patient characteristics. Seventeen consecutive patients with refractory AV nodal reentrant tachycardia underwent these procedures between December 1987 and April 1990, AV nodal skeletonization was used in the first 10 patients and the discrete perinodal cryosurgical procedure was used for the next seven consecutive patients, The intent of both procedures was to alter the perinodal tissues so as to leave one of the dual AV nodal
pathways intact. There were 10 female and seven male patients, and their ages ranged from 14 to 59 years with a mean age of 36.5 years. All the patients had highly symptomatic recurrent paroxysmal tachycardia. The most common symptoms associated with the tachycardia were palpitations, dizziness, chest pain, and syncope. Six patients had syncope as a part of their symptom complex; the remainder of the patients had dizziness, palpitations, or chest pain associated with their arrhythmia. The duration of symptoms ranged from 0.5 to 34.0 years (mean 14.5 years). The patients had multiple unsuccessful antiarrhythmic drug trials, averaging 3.3 drugs per patient (range 0 to 6). Three patients also had unsuccessful attempts at controlling their tachycardia with an antitachycardia pacemaker (Table 11). In two patients, concomitant Wolff-Parkinson-White syndrome was present. The pathways were located in the posteroseptal region and these accessory pathways were surgically ablated before surgical treatment of the AV node reentrant tachycardia. Both of these posteroseptal pathways were interrupted by means of an epicardial approach on a beating heart before institution of normothermic cardiopulmonary by-
pass." 10, II
Results Results of the operation. There were no operative deaths or unusual complications. Surgical treatment successfully eliminated the A V nodal reentrant tachycardia in aliI 7 patients, but two patients had complete A V block after the operation and required permanent pacemaker implantation. Both these patients (patient 15 and patient 16) underwent surgical dissection and skeletonization of the A V node. In addition, one of these patients had adjuvant cryoablation for the tachycardia. Injury to the nor-
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AV nodal reentrant tachycardia
I 0 39
ATRIAL
MEMBRANOUS SEPTUM
Fig. 3. Operative approach forendocardial skeletonization of AV node. Theanteroseptal and posteroseptal dissections have been completed. Theperiannular incision isextended to divide thestrip ofatrialmuscle that isstill intact. Therightatrialseptal wall is mobilized exposing the intermediate AV node. mal conduction system, resulting in heart block, did not occur in any of the patients who had the discrete perinodal cryosurgical procedure. Effects of the operation on AV nodal reentrant physiology. At postoperative electrophysiologic study, neitherechoesnor AV nodal reentrant tachycardia were inducible in any of the 17patients. The effectsof surgical therapy for A V nodal reentrant tachycardia on A V nodal antegrade and retrograde physiology have been described in this patient group.* Thirteen of 15 patients had prolonged VA conductiontime compared with baseline valuesand exhibitedcomplete VA block in the presence of intact AV conduction after the operation. The changes in the AV nodal antegrade refractoriness postoperatively were not influenced by the type of surgical technique used. Follow-up. None of the 17 patients had inducible or spontaneous AV nodal reentrant echoes or tachycardia postoperatively or during follow-up of 20.6 months (range 'Wilensky RL, Miles W, Klein LS, Mahomed Y, King RD, Zipes DP. Effects of surgery for AV nodal reentry on A V nodal physiology. Unpublished data.
Fig. 4. After completion of the right atrial septal dissection, the periannular incision isclosed with a continuous running 5-0 Prolene suture (Ethicon, Inc., Somerville, N.J.). 4 to 34). All the patients were examined by at least one of the authors after discharge from the hospital. In addition, all patients were contacted periodicallyby telephone and questionedfor any recurrence of symptomsonce they returned to the care of their referring physician. If a patient complained of palpitations postoperatively, longterm electrocardiographic recordings and arrhythmia event monitoring were undertaken. Three patients complainedof symptomssimilar to those before the operation and underwent a repeat electrophysiologic study 4 to 9 monthsafter the operation. None of the three patients had AV nodal echoesor inducibletachycardia, and their palpitations were ascribed to premature atrial or ventricular contractions. New right bundle branch block was present in three patients after the operation. One patient had a ratedependent right bundle branch block, which became apparent whilepacing at 400 msec.A secondpatient with new right bundle branch block had a normal electrocardiogram at 6 weeks'follow-up. The third patient with new right bundle branch block after the operation continued to have permanent block at follow-up. There have been no late deaths and all patients remain
The Journal of Thoracic and Cardiovascular Surgery
1040 Mahomed et ai.
SEP11JM lIS BUNDlE
1tI NODE
Fig. 5. Operative approach for identification of the His bundle with a hand-heldmapping probe.A right atriotomyexposes the atrial septum. The triangle of Koch is bounded by the tendon of Todaro, the anterior edge of the coronary sinus ostium, and the anulus of the septal leaflet of the tricuspid valve.
ENCIRCLEMENT OF AVN BY CRYOLESIONS
Discussion
Fig. 6. Operativeapproachfordiscreteperinodal cryosurgery. The first three cryolesions have been created along the tendon of Todaro beginning at the level of the coronary sinus os. The remainingcryolesions havebeenoutlined.Inset shows complete encirclement of the A V node (A VN) by a seriesof ninecryoleS10ns.
Reentry within the AV node is the most common mechanism for paroxysmal supraventricular tachycardia in human beings. Other causes of paroxysmal supraventricular tachycardia are intraatrial reentry, sinus node reentry, and arrhythmias involving an accessory pathway.12-14 The electrophysiologic substrate for A V nodal reentrant tachycardia is provided by functional longitudinal dissociation of A V nodal conduction into two pathways (dual A V nodal pathways), one of which usually has a rapid conduction velocity with a long ERP (fast pathway) and the other of which has slower conduction velocity with a shorter ERP (slow pathway) 15 (Fig. 7). It has not been clearly established whether the dual A V nodal pathways are located in the A V nodel5, 16 or whether the reentrant circuit includes the A V node and the lower atrial septum. 17, 18 Extensive animal studies17-22 and the successful results of surgical procedures that modify the perinodal tissues while preserving antegrade A V nodal conduction properties suggest that the perinodal tissues may play an important role in the maintenance of A V nodal reentrant tachycardia and implicates this portion of the atrium in the reentrant circuit. 2,4, 5,10, 11
Fortuitous surgical cure of AV nodal reentrant tachycardia in a patient with incessant symptoms after an unsuccessful attempt at surgical ablation of the A V node by Pritchett and his colleagues1heralded the possibility of developing a reproducible surgical procedure to ablate the reentrant tachycardia while preserving AV conduction. Up to that time, surgical therapy for A V nodal reentrant tachycardia refractory to antiarrhythmic drug therapy consisted of surgical cryoablation of the His bundle-' and creation of complete heart block necessitating implantation of a permanent transvenous pacemaker. This approach was subsequently replaced by catheter ablation of the His bundle.r" which obviated the need for an open cardiac operation but still necessitated pacemaker implantation for the resultant third-degree heart block. Cox and coworkers performed a series of experimental studies using a cryosurgical procedure in a canine model, and as a result of these studies the first perinodal cryosurgical procedure was performed on a human being in 1982. 3 Ross and colleagues/ subsequently reported on a surgical dissection technique in 1985. Their technique
free of recurrent A V nodal reentrant tachycardia; none has required antiarrhythmic drug therapy.
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Table II. Patient characteristics Patient No. I 2 3 4 5 6 7 8 9 10
II 12 13 14
IS 16 17 Mean
Age (yr) 47 28 41 38 40 18 23 59 41 51 31 14 41 35 47 36 30 36.5
Duration of symptoms (yr)
No. of medications
Sex
Symptoms
F F F F F F
Syncope Syncope, dizziness Palpitations, dizziness Syncope, palpitations Syncope, palpitations Palpitations, dizziness
24 22 3 4 34 15
6 3 6 3 5 5
Palpitations, dizziness Syncope, palpitations Chest pain, dizziness, palpitations Syncope Chest pain, dizziness, palpitations Palpitations, dizziness Syncope Chest pain, dizziness, palpitations Chest pain, dizziness, palpitations Chest pain, dizziness, palpitations Chest pain, dizziness, palpitations
12 12 27 I 21 5 20 33 6 0.5 8 14.5
3 3 4 2
M M F F M F F M M M M 10F 7M
Palp = Palpitations, Dizz = Dizziness, CP
Antitachy. device
Type of operation
+
Dissection Dissection Dissection Dissection Dissection Dissection (cryosurgery) Dissection Dissection Dissection Dissection Cryosurgery Cryosurgery Cryosurgery Cryosurgery Cryosurgery Cryosurgery Cryosurgery 10 Dissection 7 Cryosurgery
+
I 3 5 3 3 0
+
I 3.3
3
Follow-up (mo) 33 32 28 26 26 34 34 22 19 17 16 16 13 13 13 4 4 20.58
= Chest pain, Sync = Syncope, Diss = Dissection,Cryo = Cryosurgery.
Table III. Surgery for AV node reentrant tachycardia First author
Date
No. of patients
Johnson-'
1989
69
Cox!' Guiraudon!"
1990 1990
23 32
12-56 9-67
0 0
Mahomed
1992
17
14-59
Wood J I
1988 1989 1990 1989
5 I 3 4
Case-' Holman'?
Gartman'?
Age (yr)
Mortality 0
4-5 22-48
Success rate 93%
Reop.
Heart block
3
2 Permanent 1/3 Transient 0 2 Second-degree Wenckebach 2 Permanent 1/3 Transient (dissection) 0 0 0 0
0 3
0
100% 91% Initial 1000/0 Reoperation 1000/0
0 0 0 0
1000/0 1000/0 1000/0 1000/0
0 0 0 0
was dependent on the site of earliest retrograde atrial activation mapped intraoperatively during the tachycardia. In the majority of patients the site of earliest activation during tachycardia was at the apex of the triangle of Koch, and they designated this as type A. In the minority of patients the site of earliest activation was recorded close to the os of the coronary sinus, and they designated this type B. The two dissection techniques described by Johnson and coworkers 25,26 are designed to divide the perinodal tissues that represent either the anterolateral (type A) or posterolateral (type B) input to the AV node. In 1989, Gartman and associates'? reported on a dissection technique used in four patients that was modified
0
Surgical technique Dissection Cryosurgery Dissection I0 Dissection 7 Cryosurgery Cryosurgery Cryosurgery Cryosurgery Dissection
from Johnson's operation. Their technique included intraoperative mapping, but they performed a single dissection regardless of the mapping data during the tachycardia. A third dissection technique for ablation of AV nodal reentrant tachycardia was described by Guiraudon and colleagues 10 in 1990. This technique, used in the first 10 of our patients, is an anatomically guided procedure and is aimed at skeletonizing the AV node; it involves dissecting the AV node from most of its atrial input with the intent of altering the perinodal substrate and preventing reentry. In Johnson's series of 69 patients,25,26 72 dissections were performed. There were no operative deaths. Postoperative complications occurred in seven patients and
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Fig. 7. Electrophysiologic substrate for AV node reentrant
tachycardia is provided by functional longitudinal dissociation of AV nodeconduction into twopathways(dual AV nodepathways), one of which has a rapid conduction velocity with long ERP (fast-pathway) and the other of which has a slower conductionvelocity witha shorter ERP (slow pathway) (A). A normal atrial impulse enters the His bundle by way of the fast pathway (B). An atrial premature beat is introduced as it conducts via the slowpathway since it is blocked in the fast pathway (longer ERP) (C), The impulsecan now travel retrograde up the fast pathway to producea single echo beat or (D)set up a circuitousimpulsewith the A V node,and AV nodereentrant tachycardia results. [Modified from Cox and associates. I I ]
included pericardial effusion (one patient), venous thrombosis and pulmonary embolism (three patients), and heart block necessitating pacemaker therapy (two patients). Additionally, one third of their patients had temporary A V block lasting up to 2 weeks after the operation. Three patients (4%) had early recurrence of the arrhythmia, and two of these three patients underwent reoperation with only one being cured. The third patient had no reentrant tachycardia inducible at electrophysiologic study 6 months after the operation. The 6-month postoperative electrophysiologic study also revealed AV nodal echoes or sustained tachycardia to be inducible in II patients (10 type A, 1 type B). Only five of the 11 patients had clinical recurrences of their tachycardia. Thus the clinical cure rate was 93% at 6 months. In Guiraudon's series!" of 32 patients undergoing the skeletonization operation, there were no deaths or complications. However, three patients (9%) who had recurrence of their tachycardia required reoperation (9 to II months postoperatively) to achieve uniform success. There was no complete heart block postoperatively, but two patients had second-degree heart block with Wenckebach periods (Table III). Our results with the AV node skeletonization dissec-
tion technique reflect the reported results from Johnson and Guiraudon. We experienced no morbidity or mortality. Up to one third of our patients had transient complete heart block lasting from hours to 10 days after the operation. Additionally, two of our patients had heart block necessitating pacemaker implantation. In both of these patients the heart block occurred suddenly while we were dissecting in the vicinity of the AV node, but not directly over it. In fact, in one of these two patients the heart block occurred while we were still dissecting on the free wall of the atrium in close proximity to the atrial septum. Whether the heart block is a result of permanent injury to the A V node or His bundle, due to the dissection procedure itself, or due to tissue edema after dissection that leads to destruction of the specialized conduction system remains unclear. Both of these patients remained pacemaker dependent at long-term follow-up. By comparison, our results with the perinodal cryosurgical procedure mirrored those reported by Cox and others. In their series of 23 patients, Cox and associates II reported a 100%cure rate and no heart block. In our seven patients who had the discrete perinodal cryosurgical operation, we also achieved uniform success with a 100% cure rate and no heart block. Furthermore, we found the procedure to be reproducibly easier to perform. Haissaguerre.P' Epstein.i" and their associates have described percutaneous catheter ablation with directcurrent energy. Among the 21 patients in Haissaguerre's report, 16 patients were arrhythmia free and not receiving antiarrhythmic medications (75% success rate) after a mean follow-up of 14 months (range 7 to 42). Two patients (9.5%) had complete heart block. More recently, catheter ablative techniques with radiofrequency energy30 have been used. Although surgery is avoided by catheter techniques, the technique is new and overall results await further investigation and long-term followup. In conclusion surgical treatment for the cure of AV nodal reentrant tachycardia is highly successful with both the dissection and cryosurgical techniques. Prevention of arrhythmia recurrence and avoidance of heart block, as well as ease of applicability, have made discrete perinodal cryosurgery the surgical treatment of choice for patients with refractory AV nodal reentrant tachycardia. REFERENCES 1. Pritchett ELC, Anderson RW, BendittDG, et al. Reentry
withinthe atrioventricularnode: surgical cure with preservationof atrioventricular conduction. Circulation 1979;60: 440-6. 2. RossDL, JohnsonDC, Denniss AR, CooperMJ, Richards
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DA, Uther JB. Curative surgery for atrioventricular junctional ("AV nodal") reentrant tachycardia. J Am Coli Cardiol 1985;6:1383-92. 3. Cox JL. Surgery for cardiac arrhythmias. In: Harvey WP, ed. Current problems in cardiology. Chicago: Year Book, 1983:24. 4. Cox JL, Holman WL, Cain ME. Cryosurgical treatment of atrioventricular node reentrant tachycardia. Circulation 1987;76:1329-36. 5. Guiraudon GM, Klein GJ, Sharma AD, Vee R, McLellan DG. Surgical treatment of supraventricular tachycardia: a five year experience. PACE 1986;9:1376-80. 6. Josephson ME, Seides SF. Clinical cardiac electrophysiology: techniques and interpretations. Philadelphia: Lea & Febiger, 1979:1963. 7. GuiraudonGM,KleinGJ,SharmaAD, YeeR,PinedaEA, McLellan DG. Surgical approach to anterior septal accessory pathways in 20 patients with the Wolff-ParkinsonWhite syndrome. Eur J Cardiothorac Surg 1988;2:201-6. 8. Guiraudon G M, Klein GJ, Sharma AD, Jones DL, McLellan DG. Surgical ablation of posterior septal accessory pathways in the Wolff-Parkinson-White syndrome by a closed heart technique. J THORAC CARDIOVASC SURG 1986;92:406-13. 9. Mahomed Y, King RD, Zipes DP, et al. Surgical division of Wolff-Parkinson-White pathways utilizing the closedheart technique: a 2-year experience in 47 patients. Ann Thorac Surg 1988;45:495-504. 10. Guiraudon GM, Klein GJ, Sharma AD, Vee R, Kaushik RR, Fujimural D. Skeletonization of the atrioventricular node for AV node reentrant tachycardia: experience with 32 patients. Ann Thorac Surg 1990;49:565-73. II. Cox JL, Ferguson TB Jr, Lindsay BD, Cain ME. Perinodal cryosurgery for atrioventricular node reentry tachycardia in 23 patients. J THORAC CARDIOVASC SURG 1990;99:44050. 12. Akhtar M. Atrioventricular node reentry. Circulation 1987;75:26-30. 13. Zipes DP. Specific arrhythmias: diagnosis and treatment. In: Braunwald E, ed. Heart disease: a textbook of cardiovascular medicine. WB Saunders 1988:65-76. 14. Miles WM, Zipes DP. Preexcitation syndromes. In: Hurst JW, ed. Current therapy in cardiovascular disease. B.c. Decker, Inc. [In press]. 15. Mendez C, Moe GK. Demonstration of a dual AV nodal conduction system in the isolated rabbit heart. Circ Res 1966;19:378-93. 16. Janse MJ, van Capelle FJL, Freud GE, Durrer D. Circus movement within the AV node as a basis for supraventricular tachycardia as shown by multiple microelectrode recording in the isolated rabbit heart. Circ Res 1971;28: 403-14. 17. Josephson ME, Kastor JA. Paroxysmal supraventricular tachycardia: Is the atrium a necessary link? Circulation 1976;54:430-5. 18. Iinuma H, Dreifus LS, Mazgalev T, Price R, Michelson
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19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
1 04 3
EL. Role of the perinodal region in atrioventricular nodal reentry: evidence in an isolated rabbit heart preparation. J Am Coli Cardiol 1983;2:465-73. Holman WL, Ikeshita M, Lease JG, Smith PK, Ferguson TB Jr, Cox JL. Elective prolongation of atrioventricular conduction by multiple cryolesions. J THORAC CARDlOVASC SURG 1982;84:554-9. Holman WL, Ikeshita M, Lease JG, Ferguson TB Jr, Lofland GK, Cox JL. Alteration of antegrade atrioventricular conduction by cryoablation of periatrioventricular nodal tissue. J THORAC CARDIOVASC SURG 1984;88:67-75. Holman WL, Ikeshita M, Lease JG, Smith PK, Lofland GK, Cox JL. Cryosurgical modification of retrograde atrioventricular conduction: implications for the surgical treatment of atrioventricular nodal reentry tachycardia. J THORAC CARDIOVASC SURG 1986;91:826-34. Holman WL, Hackel DB, Lease JG, Ikeshita M, Cox JL. Cryosurgical ablation of atrioventricular nodal reentry: histologic localization of the proximal common pathway. Circulation 1988;79:1356-62. Sealy WC, Gallagher JJ, Kasell J. His bundle interruption for control of inappropriate ventricular responses to atrial arrhythmias. Ann Thorac Surg 1981;32:429-38. Scheinman MM, Morady F, Hess DS, Gonzalez R. Catheter induced ablation of the atrioventricular junction to control refractory supraventricular arrhythmias. JAMA 1982;248:851-5. Johnson DC, Nunn GR, Meldrum-Hanna W. Surgery for atrioventricular node reentry tachycardia: the surgical dissection technique. Semin Thorac Cardiovasc Surg 1989;1: 53-7. Johnson DC, Nunn GR, Richards DA, Uther JB, Ross DL. Surgical therapy for supraventricular tachycardia: a potential curable disorder. J THORAC CARDIOVASC SURG 1987;93:913-8. Gartman DM, Bardy GH, Williams AB, Ivey TD. Direct surgical treatment of atrioventricular node reentrant tachycardia. J THORAC CARDIOVASC SURG 1989;98:63-72. Haissaguerre M, Warin JF, Lemetayer P, Sauodi N, Guillem JP, Blanchot P. Closed-chest ablation of retrograde conduction in patients with atrioventricular nodal reentrant tachycardia. N Engl J Moo 1989;320:426-33. Epstein LM, Scheinman MM, Langberg JJ, Chilson D, Goldbery HR, Griffin J'C, Percutaneous catheter modification of the atrioventricular node: a potential cure for atrioventricular node reentrant tachycardia. Circulation 1989; 80:757-68. Roman CA, Wang X, Friday KS, et al. Catheter technique for selectiveablation of slowpathway in AV nodal reentrant tachycardia [Abstract]. PACE 1990;13:498. Wood DL, Hammil SC, Porter CBJ, et al. Cryosurgical modification of atrioventricular conduction for treatment of atrioventricular node reentrant tachycardia. Mayo Clin Proc 1988;63:988-92. Holman WL. Paroxysmal supraventricular tachycardia due to atrioventricular nodal reentry: electrophysiologic
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mechanism and surgical therapy. Cardiac Surg State of Art Rev 1990;4:175-95. 33. Case LL, Crawford FA, Gillette PC, et al. Successful surgery for atrioventricular reentrant tachycardia in a small child. Am Heart J 1989;116:187-9.
Discussion Dr. Miguel Barbero-Marcial (Sao Paulo, Brazil). At the Heart Institute in Sao Paulo, Brazil, since 1987, we have been using a different surgical approach to treat this kind of tachycardia-posterior disconnection of the AV node. Our preliminary results were published in 1988, in Journal ofElectrophysiology. This approach is almost the same as the one that Dr. Sealy proposed for the section of posteroseptal Kent bundles. There is no dissection anterior to the AV node. This procedure is done with cardioplegic arrest. We obtained a 96% success rate in 25 patients. In only one of the 25 patients was the postoperative electrophysiologic study able to induce AV node reentrant tachycardia. There were no complications or deaths. In conclusion, this surgical technique is a nonelectrophysiologically guided approach and therefore the collaboration of the electrophysiologist is not necessary in the operating room. The postoperative AV node conduction remains intact, and this technique demonstrated that a limited and restricted posteroseptal dissection in the same way that Dr. Sealy described it many years ago was enough to obtain success. Dr. Mahomed. Dr. Barbero- Marcial's results reflect those of others who use dissection techniques. Dr. Guiraudon has an initial success rate of 91 %, and long-term follow-up in Dr. Johnson's series reveals a success rate of 83%. Various authors have reported on the cryosurgical technique, and uniformly there has been a 100% success rate with this approach.
The Journal of Thoracic and Cardiovascular Surgery
Dr. James L. Cox (St. Louis, Mo.). The important point to recognize is that there are two types of AV node reentry, one in which the reentrant circuit is located posteriorly in the triangle of Koch (90% to 95%) and the other in which the reentrant circuit is located anteriorly (5% to 10%). The results presented by Dr. Mahomed, in which the surgical dissection had a 20% incidence of heart block, is characteristic of the surgical dissection techniques. The other extreme, in which the reentrant circuit is missed in 4% to 10% of patients, is also quite characteristic, as experienced in Dr. Barbero-Marcial's series. These failures are almost certainly due to the fact that the dissection, which is similar to the surgical dissection technique for AV node reentry, for posteroseptal pathways in the Wolff-Parkinson-White syndrome does not address the anterior type of AV node reentry. Unfortunately, to divide that last 5% to 10% of reentrant circuits that occur anteriorly, additional dissection anteriorly is required, and therein lies the problem of heart block. If you dissect in both areas (anterior and posterior), then you pay the price of a significant level of heart block after the operation. I would like to ask Dr. Mahomed if he could confirm that postoperative heart block in his patients resulted from the anterior portion of the dissection. Dr. Mahomed. That is precisely what happened in both patients. The heart block occurred at the time that we were performing the dissection in the anteroseptal region. I will add one other note regarding the two techniques. The perinodal cryosurgical technique is a straightforward and simple approach to this problem. The dissection technique requires a lot more attention to detail and, for those not familiar with this particular area, a considerable amount of study. I consider the dissection technique a much superior way of approaching refractory AV node reentrant tachycardia.
h e first successful surgical interruption of atrioventricular (AV) nodal reentrant tachycardia occurred forFrom the Departments of Surgery" and Medicine," Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Ind. Read at the Seventy-first Annual Meeting of The American Association for Thoracic Surgery, Washington, D.C., May 6-8, 1991. Address for reprints: Yousuf Mahomed, MD, Indiana University School of Medicine, Department of Surgery, 545 Barnhill Dr., Emerson Hall 212, Indianapolis, IN 46202.
12/6/39846
tuitously after a failed attempt at surgical ablation of the AV node in a patient with incessant AV nodal reentrant tachycardia. I Ross and associates/ subsequently demonstrated the ability to cure AV nodal reentrant tachycardia by surgical dissection with a high success rate and while preserving AV conduction. The operation was based on intraoperative mapping of the retrograde limb of the reentrant circuit during AV nodal reentrant tachycardia. Cox and colleagues- 4 presented a technique in which cryosurgery is used to modify the perinodal tissues along the perimeter of the triangle of Koch with excellent
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Table I. Preoperative electrophysiologic characteristics
Patient No. I
2 3 4 5 6 7 8 9 10
Discontinuous AVN curve
AVNRT cycle length (msec)
+ + +
335 300 420 300 255 350 270 350 320 290 275 420 340 370 300 200 300 323
+ + + + +
II
12 13 14 15 16 17 Mean value
+ + + +11 -6
Shortest VA interval
10 -20 75 0 -10 0 35 0 0 45 -10
85 45 -15 -20 25 40 16.75
Preop. incremental increase in retrograde conduction (msec)
60 40 Fixed
40 20 50 30 10
20 Fixed
20 Fixed
N/A
Fixed
40 60 50
AVN, AV node; AVNRT, AV node reentrant tachycardia; N/A, not applicable.
results, Cryosurgery was chosen because of its unique ability to obtund electrical activity before causing cell death. Recently, Guiraudon and coworkers' presented a dissection technique, which is an anatomically guided "skeletonization" of the AV node from its atrial input, resulting in successful cure of the tachycardia while preserving A V conduction. The purpose of this study is to report our experience with both the A V node skeletonization procedure and the discrete perinodal cryosurgical procedure in 17 consecutive patients with medically refractory A V nodal reentrant tachycardia. Methods Preoperative electrophysiologic study. All 17 patients who underwent surgical treatment for AV nodal reentrant tachycardia had electrophysiologic studies performed preoperatively after informed written consent was obtained. Preoperative electrophysiologic testing was done with the patient in the drug-free, nonsedated, postabsorptive state. Standard 6F multipolar electrode catheters, placed in the high right atrium, in the His bundle region, in the right ventricular apex, and in the coronary sinus for selected patients, were used. In addition to the intracardiac electrocardiograms, surface electrocardiographic leads I, II, III, and VI were recorded simultaneously (PPG VR-16) at paper speeds of 50 to ISO rum/sec. The extrastimulus technique was used to measure the AV nodal effective refractory period (ERP) at 400, 500, 600, and if necessary 700 msec pacing cycle lengths, by means of a stepwise 10 msec decrease in SI and S2. In addition, AV function and ventriculoatrial (VA) function were measured at decreasing SI intervals to the point at which 1:1 conduction failed. Tachycar-
dia was induced by introducing single and double atrial or ventricular extrastimuli. Isoproterenol was used to facilitate tachycardia induction if needed (Table I). Diagnosis of AV nodal reentrant tachycardia. The diagnosis of AV nodal reentrant tachycardia was based on initiation of the tachycardia dependent on a critical delay in the conduction time between the atrium and His bundle (AH interval) and a normal retrograde activation pattern during tachycardia with the earliest activation recorded at the His bundle catheter and termination of the tachycardia by AV nodal block. Criteria that were considered useful, but not mandatory, for the diagnosis of AV nodal reentrant tachycardia included (I) the presence of discontinuous AV nodal conduction curves in response to atrial extrastimuli and (2) a shortest VA interval less than 60 msec; accessory AV connections were excluded in all patients." Intraoperative electrophysiologic study. Intraoperative electrophysiologic studies were obtained with quadripolar, epicardial plaque electrodes sutured to the epicardial surfaces of the right atrium and the right ventricle. These plaque electrodes served both for pacing and for recording atrial and ventricular electrograms. Stimulation studies were undertaken to eliminate the coexistence of concealed. accessory AV conduction and to confirm the presence of AV nodal reentrant tachycardia. Mapping was not necessary to perform either the skeletonization procedure or the discrete perinodal cryosurgical procedure, since both of these methods are anatomically guided. After a right atriotomy was done, a hand-held mapping probe (interelectrode distance 1.5 mm) was used to identify and localize the His bundle. During both the surgical skeletonization procedure and the discrete perinodal cryosurgical procedure, atrial pacing was instituted at a constant cycle length and AV conduction was closely monitored on a beat-to-beat basis with an oscilloscope. After completion of both the skeletonization and perinodal cryosurgical procedure, but before separation from cardiopul-
Volume 104 Number 4 October 1992
monary bypass, a postintervention electrophysiologic study was undertaken in which incremental atrial and ventricular pacing and programmed atrial and ventricular stimulation were used to assess AV conduction and to attempt to induce echo beats or AV nodal reentrant tachycardia. Postoperative electrophysiologic study. Postoperative electrophysiologicstudies were performed 6.5 days (mean) after the operation (range 5 to 8 days) with two pairs of atrial and one pair of right ventricular temporary epicardial pacemaker electrodes placed during the operation. Measurements were recorded in a similar fashion as in the preoperative studies. Surgical technique. The heart was exposed through a standard median sternotomy incision (n = 15) or through a bilateral submammary incision (n = 2) when the latter was requested for cosmetic reasons. Quadripolar epicardial plaque electrodes were sutured to the right atrium and the right ventricle. With the use of incremental pacing and extrastimulus testing, as previouslynoted, the AV nodal reentrant tachycardia was induced and terminated and a ring map of the AV groove was performed to exclude a concealed accessory pathway. Normothermic cardiopulmonary bypass was begun with aortic and bicaval cannulation. The venous cannulas were placed through juxtacaval pursestring sutures so as to gain maximal exposure to the right atrial chamber. Both the superior and inferior venae cavae were snared with tapes. The heart was then electrically fibrillated and a right atriotomy was performed. In the skeletonization procedure, the right atriotomy was placed along the periannular region of the exposed tricuspid anulus in the anteroseptal region. With the cryosurgical technique, a lateral atriotomy was performed. The atrial septum was then gently inspected and probed to exclude the presence of an atrial septal defect or a patent foramen ovale; if such was present, it was closed. The heart was then defibrillated and the remainder of the procedure was performed on a normothermic beating heart. The skeletonization operation. A V node skeletonization was guided by the following anatomic landmarks: the atrial membranous septum, the posterosuperior process of the left ventricle, the tendon of Todaro, and the os of the coronary sinus. The technique involvedthree separate steps: (I) an anteroseptal epicardial dissection, (2) a posteroseptal epicardial dissection, and (3) endocardial exposure of the intermediate AV node by dissection of the lower right atrial septum. The epicardial anteroseptal dissection was performed by mobilizing the AV fat pad in the right coronary fossa and exposingthe tricuspid valve anulus. The posteroseptal epicardial dissection was then performed by mobilizing the right ventricular and right atrial-left ventricular fat pad and exposing the AV junction. The dissection was extended well into the posteroseptal region, exposing the inferomedial right atrial wall and the posterosuperior process of the left ventriclel? (Figs. I and 2). Normothermic cardiopulmonary bypass was instituted after completion of the epicardial dissection, and skeletonization of the intermediate AV node was then performed endocardially. The periannular right atriotomy was extended to the atrial membranous septum. This incision was carefully extended endocardially along the septal portion of the tricuspid anulus to terminate at the point of dissection of the previously exposed posteroseptal region. The septal atrial wall was carefully mobilized to expose the intermediate AV node, which was identifiable by pale yellow fibers. The tendon of Todaro constituted the
A V nodal reentrant tachycardia
10 3 7
Fig. 1. Surgical approach for anteroseptal AV fat pad dissection. The right AV fat pad has been dissected in the right coronary fossa exposing the white fibrous AV ring of the tricuspid anulus. RA, Right atrium; RV, right ventricle; AV, atrioventricular. posterior limits of dissection and the os of the coronary sinus the inferior limits of dissection. Surgical skeletonization of the AV node interrupted the superficial and posterior atrial inputs ofthe AV node leaving only the deep inputs intact'" (Figs. 3 and 4). The discrete perinodal cryosurgical operation. The anatomic landmarks guiding the perinodal cryosurgical procedure were the His bundle and the triangle of Koch. The triangle of Koch is bounded by the tendon of Todaro, the anterior edge of the coronary sinus ostium, and the anulus of the septal leaflet of the tricuspid valve (Fig. 5). The cryosurgical procedure was designed to alter the perinodal tissues of the AV node by creating a series of cryolesions along the borders of Koch's triangle. After institution of normothermic cardiopulmonary bypass, a right atriotomy was performed. The His bundle was identified with a hand-held probe. The heart was atrially paced and AV conduction was monitored very closely. A dry operative field was obtained by placement of flexible intracardiac sump catheters in the os of the coronary sinus and through the tricuspid valve orifice to aspirate blood return from these areas. A 3 mm diameter cryoprobe (Frigitronics, Inc., Shelton, Conn.) was used to create a series of cryolesions along the perimeter of Koch's triangle. The cryoprobe was cooled to -60 0 C and held at each position for 2 minutes to assure cell death.
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Surgery
Fig. 2. Surgical approach for posteroseptal AV fat pad dissection. The right ventricular and right atrial-left ventricular AV fat pad has been dissected exposing the white (tricuspid anulus) and the posterosuperior process of the left ventricle.
The series of overlapping cryolesions were created beginning inferiorly at the edge of the coronary sinus os and progressing cephalad along the tendon of Todaro, then across the tricuspid valve anulus from the coronary sinus os inferiorly to the His bundle region superiorly, and finally along the coronary sinus os (Fig. 6). A total of nine cryolesions were usually necessary to completely cryoablate the perimeter of the triangle of Koch. Rarely, additional cryolesions were placed inside the triangle to cryoablate as much atrial tissue as possible while preserving AV conduction." If AV conduction prolonged and heart block occurred during cryothermic exposure, cooling was immediately stopped and the cryoprobe flushed with warm saline to facilitate its removal; the cryolesion itself was then further gently irrigated with the warm saline. AV conduction usually returned within 30 to 60 seconds and the prolonged AV interval returned to baseline. Lengthening of the AV interval and transient heart block was most likely to occur during application of the cryoprobe along the tricuspid valve anulus near the His bundle. If lengthening of the AV interval and heart block did occur, cryothermia was immediately terminated. After resumption of A V conduction and return of the AV interval to baseline, the cryoprobe was reapplied, moving it more closely toward the anulus for 2 minutes at each site. A full 2 minutes of cryothermic exposure was necessary at each location to assure cell death while avoiding heart block. The unique ability of cryothermia to obtund cellular activity before causing cell death permitted this approach.f- II Patient characteristics. Seventeen consecutive patients with refractory AV nodal reentrant tachycardia underwent these procedures between December 1987 and April 1990, AV nodal skeletonization was used in the first 10 patients and the discrete perinodal cryosurgical procedure was used for the next seven consecutive patients, The intent of both procedures was to alter the perinodal tissues so as to leave one of the dual AV nodal
pathways intact. There were 10 female and seven male patients, and their ages ranged from 14 to 59 years with a mean age of 36.5 years. All the patients had highly symptomatic recurrent paroxysmal tachycardia. The most common symptoms associated with the tachycardia were palpitations, dizziness, chest pain, and syncope. Six patients had syncope as a part of their symptom complex; the remainder of the patients had dizziness, palpitations, or chest pain associated with their arrhythmia. The duration of symptoms ranged from 0.5 to 34.0 years (mean 14.5 years). The patients had multiple unsuccessful antiarrhythmic drug trials, averaging 3.3 drugs per patient (range 0 to 6). Three patients also had unsuccessful attempts at controlling their tachycardia with an antitachycardia pacemaker (Table 11). In two patients, concomitant Wolff-Parkinson-White syndrome was present. The pathways were located in the posteroseptal region and these accessory pathways were surgically ablated before surgical treatment of the AV node reentrant tachycardia. Both of these posteroseptal pathways were interrupted by means of an epicardial approach on a beating heart before institution of normothermic cardiopulmonary by-
pass." 10, II
Results Results of the operation. There were no operative deaths or unusual complications. Surgical treatment successfully eliminated the A V nodal reentrant tachycardia in aliI 7 patients, but two patients had complete A V block after the operation and required permanent pacemaker implantation. Both these patients (patient 15 and patient 16) underwent surgical dissection and skeletonization of the A V node. In addition, one of these patients had adjuvant cryoablation for the tachycardia. Injury to the nor-
Volume 104 Number 4 October 1992
AV nodal reentrant tachycardia
I 0 39
ATRIAL
MEMBRANOUS SEPTUM
Fig. 3. Operative approach forendocardial skeletonization of AV node. Theanteroseptal and posteroseptal dissections have been completed. Theperiannular incision isextended to divide thestrip ofatrialmuscle that isstill intact. Therightatrialseptal wall is mobilized exposing the intermediate AV node. mal conduction system, resulting in heart block, did not occur in any of the patients who had the discrete perinodal cryosurgical procedure. Effects of the operation on AV nodal reentrant physiology. At postoperative electrophysiologic study, neitherechoesnor AV nodal reentrant tachycardia were inducible in any of the 17patients. The effectsof surgical therapy for A V nodal reentrant tachycardia on A V nodal antegrade and retrograde physiology have been described in this patient group.* Thirteen of 15 patients had prolonged VA conductiontime compared with baseline valuesand exhibitedcomplete VA block in the presence of intact AV conduction after the operation. The changes in the AV nodal antegrade refractoriness postoperatively were not influenced by the type of surgical technique used. Follow-up. None of the 17 patients had inducible or spontaneous AV nodal reentrant echoes or tachycardia postoperatively or during follow-up of 20.6 months (range 'Wilensky RL, Miles W, Klein LS, Mahomed Y, King RD, Zipes DP. Effects of surgery for AV nodal reentry on A V nodal physiology. Unpublished data.
Fig. 4. After completion of the right atrial septal dissection, the periannular incision isclosed with a continuous running 5-0 Prolene suture (Ethicon, Inc., Somerville, N.J.). 4 to 34). All the patients were examined by at least one of the authors after discharge from the hospital. In addition, all patients were contacted periodicallyby telephone and questionedfor any recurrence of symptomsonce they returned to the care of their referring physician. If a patient complained of palpitations postoperatively, longterm electrocardiographic recordings and arrhythmia event monitoring were undertaken. Three patients complainedof symptomssimilar to those before the operation and underwent a repeat electrophysiologic study 4 to 9 monthsafter the operation. None of the three patients had AV nodal echoesor inducibletachycardia, and their palpitations were ascribed to premature atrial or ventricular contractions. New right bundle branch block was present in three patients after the operation. One patient had a ratedependent right bundle branch block, which became apparent whilepacing at 400 msec.A secondpatient with new right bundle branch block had a normal electrocardiogram at 6 weeks'follow-up. The third patient with new right bundle branch block after the operation continued to have permanent block at follow-up. There have been no late deaths and all patients remain
The Journal of Thoracic and Cardiovascular Surgery
1040 Mahomed et ai.
SEP11JM lIS BUNDlE
1tI NODE
Fig. 5. Operative approach for identification of the His bundle with a hand-heldmapping probe.A right atriotomyexposes the atrial septum. The triangle of Koch is bounded by the tendon of Todaro, the anterior edge of the coronary sinus ostium, and the anulus of the septal leaflet of the tricuspid valve.
ENCIRCLEMENT OF AVN BY CRYOLESIONS
Discussion
Fig. 6. Operativeapproachfordiscreteperinodal cryosurgery. The first three cryolesions have been created along the tendon of Todaro beginning at the level of the coronary sinus os. The remainingcryolesions havebeenoutlined.Inset shows complete encirclement of the A V node (A VN) by a seriesof ninecryoleS10ns.
Reentry within the AV node is the most common mechanism for paroxysmal supraventricular tachycardia in human beings. Other causes of paroxysmal supraventricular tachycardia are intraatrial reentry, sinus node reentry, and arrhythmias involving an accessory pathway.12-14 The electrophysiologic substrate for A V nodal reentrant tachycardia is provided by functional longitudinal dissociation of A V nodal conduction into two pathways (dual A V nodal pathways), one of which usually has a rapid conduction velocity with a long ERP (fast pathway) and the other of which has slower conduction velocity with a shorter ERP (slow pathway) 15 (Fig. 7). It has not been clearly established whether the dual A V nodal pathways are located in the A V nodel5, 16 or whether the reentrant circuit includes the A V node and the lower atrial septum. 17, 18 Extensive animal studies17-22 and the successful results of surgical procedures that modify the perinodal tissues while preserving antegrade A V nodal conduction properties suggest that the perinodal tissues may play an important role in the maintenance of A V nodal reentrant tachycardia and implicates this portion of the atrium in the reentrant circuit. 2,4, 5,10, 11
Fortuitous surgical cure of AV nodal reentrant tachycardia in a patient with incessant symptoms after an unsuccessful attempt at surgical ablation of the A V node by Pritchett and his colleagues1heralded the possibility of developing a reproducible surgical procedure to ablate the reentrant tachycardia while preserving AV conduction. Up to that time, surgical therapy for A V nodal reentrant tachycardia refractory to antiarrhythmic drug therapy consisted of surgical cryoablation of the His bundle-' and creation of complete heart block necessitating implantation of a permanent transvenous pacemaker. This approach was subsequently replaced by catheter ablation of the His bundle.r" which obviated the need for an open cardiac operation but still necessitated pacemaker implantation for the resultant third-degree heart block. Cox and coworkers performed a series of experimental studies using a cryosurgical procedure in a canine model, and as a result of these studies the first perinodal cryosurgical procedure was performed on a human being in 1982. 3 Ross and colleagues/ subsequently reported on a surgical dissection technique in 1985. Their technique
free of recurrent A V nodal reentrant tachycardia; none has required antiarrhythmic drug therapy.
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AV nodal reentrant tachycardia
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Table II. Patient characteristics Patient No. I 2 3 4 5 6 7 8 9 10
II 12 13 14
IS 16 17 Mean
Age (yr) 47 28 41 38 40 18 23 59 41 51 31 14 41 35 47 36 30 36.5
Duration of symptoms (yr)
No. of medications
Sex
Symptoms
F F F F F F
Syncope Syncope, dizziness Palpitations, dizziness Syncope, palpitations Syncope, palpitations Palpitations, dizziness
24 22 3 4 34 15
6 3 6 3 5 5
Palpitations, dizziness Syncope, palpitations Chest pain, dizziness, palpitations Syncope Chest pain, dizziness, palpitations Palpitations, dizziness Syncope Chest pain, dizziness, palpitations Chest pain, dizziness, palpitations Chest pain, dizziness, palpitations Chest pain, dizziness, palpitations
12 12 27 I 21 5 20 33 6 0.5 8 14.5
3 3 4 2
M M F F M F F M M M M 10F 7M
Palp = Palpitations, Dizz = Dizziness, CP
Antitachy. device
Type of operation
+
Dissection Dissection Dissection Dissection Dissection Dissection (cryosurgery) Dissection Dissection Dissection Dissection Cryosurgery Cryosurgery Cryosurgery Cryosurgery Cryosurgery Cryosurgery Cryosurgery 10 Dissection 7 Cryosurgery
+
I 3 5 3 3 0
+
I 3.3
3
Follow-up (mo) 33 32 28 26 26 34 34 22 19 17 16 16 13 13 13 4 4 20.58
= Chest pain, Sync = Syncope, Diss = Dissection,Cryo = Cryosurgery.
Table III. Surgery for AV node reentrant tachycardia First author
Date
No. of patients
Johnson-'
1989
69
Cox!' Guiraudon!"
1990 1990
23 32
12-56 9-67
0 0
Mahomed
1992
17
14-59
Wood J I
1988 1989 1990 1989
5 I 3 4
Case-' Holman'?
Gartman'?
Age (yr)
Mortality 0
4-5 22-48
Success rate 93%
Reop.
Heart block
3
2 Permanent 1/3 Transient 0 2 Second-degree Wenckebach 2 Permanent 1/3 Transient (dissection) 0 0 0 0
0 3
0
100% 91% Initial 1000/0 Reoperation 1000/0
0 0 0 0
1000/0 1000/0 1000/0 1000/0
0 0 0 0
was dependent on the site of earliest retrograde atrial activation mapped intraoperatively during the tachycardia. In the majority of patients the site of earliest activation during tachycardia was at the apex of the triangle of Koch, and they designated this as type A. In the minority of patients the site of earliest activation was recorded close to the os of the coronary sinus, and they designated this type B. The two dissection techniques described by Johnson and coworkers 25,26 are designed to divide the perinodal tissues that represent either the anterolateral (type A) or posterolateral (type B) input to the AV node. In 1989, Gartman and associates'? reported on a dissection technique used in four patients that was modified
0
Surgical technique Dissection Cryosurgery Dissection I0 Dissection 7 Cryosurgery Cryosurgery Cryosurgery Cryosurgery Dissection
from Johnson's operation. Their technique included intraoperative mapping, but they performed a single dissection regardless of the mapping data during the tachycardia. A third dissection technique for ablation of AV nodal reentrant tachycardia was described by Guiraudon and colleagues 10 in 1990. This technique, used in the first 10 of our patients, is an anatomically guided procedure and is aimed at skeletonizing the AV node; it involves dissecting the AV node from most of its atrial input with the intent of altering the perinodal substrate and preventing reentry. In Johnson's series of 69 patients,25,26 72 dissections were performed. There were no operative deaths. Postoperative complications occurred in seven patients and
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The Journal of Thoracic and Cardiovascular Surgery
Mahomed et al.
Fig. 7. Electrophysiologic substrate for AV node reentrant
tachycardia is provided by functional longitudinal dissociation of AV nodeconduction into twopathways(dual AV nodepathways), one of which has a rapid conduction velocity with long ERP (fast-pathway) and the other of which has a slower conductionvelocity witha shorter ERP (slow pathway) (A). A normal atrial impulse enters the His bundle by way of the fast pathway (B). An atrial premature beat is introduced as it conducts via the slowpathway since it is blocked in the fast pathway (longer ERP) (C), The impulsecan now travel retrograde up the fast pathway to producea single echo beat or (D)set up a circuitousimpulsewith the A V node,and AV nodereentrant tachycardia results. [Modified from Cox and associates. I I ]
included pericardial effusion (one patient), venous thrombosis and pulmonary embolism (three patients), and heart block necessitating pacemaker therapy (two patients). Additionally, one third of their patients had temporary A V block lasting up to 2 weeks after the operation. Three patients (4%) had early recurrence of the arrhythmia, and two of these three patients underwent reoperation with only one being cured. The third patient had no reentrant tachycardia inducible at electrophysiologic study 6 months after the operation. The 6-month postoperative electrophysiologic study also revealed AV nodal echoes or sustained tachycardia to be inducible in II patients (10 type A, 1 type B). Only five of the 11 patients had clinical recurrences of their tachycardia. Thus the clinical cure rate was 93% at 6 months. In Guiraudon's series!" of 32 patients undergoing the skeletonization operation, there were no deaths or complications. However, three patients (9%) who had recurrence of their tachycardia required reoperation (9 to II months postoperatively) to achieve uniform success. There was no complete heart block postoperatively, but two patients had second-degree heart block with Wenckebach periods (Table III). Our results with the AV node skeletonization dissec-
tion technique reflect the reported results from Johnson and Guiraudon. We experienced no morbidity or mortality. Up to one third of our patients had transient complete heart block lasting from hours to 10 days after the operation. Additionally, two of our patients had heart block necessitating pacemaker implantation. In both of these patients the heart block occurred suddenly while we were dissecting in the vicinity of the AV node, but not directly over it. In fact, in one of these two patients the heart block occurred while we were still dissecting on the free wall of the atrium in close proximity to the atrial septum. Whether the heart block is a result of permanent injury to the A V node or His bundle, due to the dissection procedure itself, or due to tissue edema after dissection that leads to destruction of the specialized conduction system remains unclear. Both of these patients remained pacemaker dependent at long-term follow-up. By comparison, our results with the perinodal cryosurgical procedure mirrored those reported by Cox and others. In their series of 23 patients, Cox and associates II reported a 100%cure rate and no heart block. In our seven patients who had the discrete perinodal cryosurgical operation, we also achieved uniform success with a 100% cure rate and no heart block. Furthermore, we found the procedure to be reproducibly easier to perform. Haissaguerre.P' Epstein.i" and their associates have described percutaneous catheter ablation with directcurrent energy. Among the 21 patients in Haissaguerre's report, 16 patients were arrhythmia free and not receiving antiarrhythmic medications (75% success rate) after a mean follow-up of 14 months (range 7 to 42). Two patients (9.5%) had complete heart block. More recently, catheter ablative techniques with radiofrequency energy30 have been used. Although surgery is avoided by catheter techniques, the technique is new and overall results await further investigation and long-term followup. In conclusion surgical treatment for the cure of AV nodal reentrant tachycardia is highly successful with both the dissection and cryosurgical techniques. Prevention of arrhythmia recurrence and avoidance of heart block, as well as ease of applicability, have made discrete perinodal cryosurgery the surgical treatment of choice for patients with refractory AV nodal reentrant tachycardia. REFERENCES 1. Pritchett ELC, Anderson RW, BendittDG, et al. Reentry
withinthe atrioventricularnode: surgical cure with preservationof atrioventricular conduction. Circulation 1979;60: 440-6. 2. RossDL, JohnsonDC, Denniss AR, CooperMJ, Richards
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DA, Uther JB. Curative surgery for atrioventricular junctional ("AV nodal") reentrant tachycardia. J Am Coli Cardiol 1985;6:1383-92. 3. Cox JL. Surgery for cardiac arrhythmias. In: Harvey WP, ed. Current problems in cardiology. Chicago: Year Book, 1983:24. 4. Cox JL, Holman WL, Cain ME. Cryosurgical treatment of atrioventricular node reentrant tachycardia. Circulation 1987;76:1329-36. 5. Guiraudon GM, Klein GJ, Sharma AD, Vee R, McLellan DG. Surgical treatment of supraventricular tachycardia: a five year experience. PACE 1986;9:1376-80. 6. Josephson ME, Seides SF. Clinical cardiac electrophysiology: techniques and interpretations. Philadelphia: Lea & Febiger, 1979:1963. 7. GuiraudonGM,KleinGJ,SharmaAD, YeeR,PinedaEA, McLellan DG. Surgical approach to anterior septal accessory pathways in 20 patients with the Wolff-ParkinsonWhite syndrome. Eur J Cardiothorac Surg 1988;2:201-6. 8. Guiraudon G M, Klein GJ, Sharma AD, Jones DL, McLellan DG. Surgical ablation of posterior septal accessory pathways in the Wolff-Parkinson-White syndrome by a closed heart technique. J THORAC CARDIOVASC SURG 1986;92:406-13. 9. Mahomed Y, King RD, Zipes DP, et al. Surgical division of Wolff-Parkinson-White pathways utilizing the closedheart technique: a 2-year experience in 47 patients. Ann Thorac Surg 1988;45:495-504. 10. Guiraudon GM, Klein GJ, Sharma AD, Vee R, Kaushik RR, Fujimural D. Skeletonization of the atrioventricular node for AV node reentrant tachycardia: experience with 32 patients. Ann Thorac Surg 1990;49:565-73. II. Cox JL, Ferguson TB Jr, Lindsay BD, Cain ME. Perinodal cryosurgery for atrioventricular node reentry tachycardia in 23 patients. J THORAC CARDIOVASC SURG 1990;99:44050. 12. Akhtar M. Atrioventricular node reentry. Circulation 1987;75:26-30. 13. Zipes DP. Specific arrhythmias: diagnosis and treatment. In: Braunwald E, ed. Heart disease: a textbook of cardiovascular medicine. WB Saunders 1988:65-76. 14. Miles WM, Zipes DP. Preexcitation syndromes. In: Hurst JW, ed. Current therapy in cardiovascular disease. B.c. Decker, Inc. [In press]. 15. Mendez C, Moe GK. Demonstration of a dual AV nodal conduction system in the isolated rabbit heart. Circ Res 1966;19:378-93. 16. Janse MJ, van Capelle FJL, Freud GE, Durrer D. Circus movement within the AV node as a basis for supraventricular tachycardia as shown by multiple microelectrode recording in the isolated rabbit heart. Circ Res 1971;28: 403-14. 17. Josephson ME, Kastor JA. Paroxysmal supraventricular tachycardia: Is the atrium a necessary link? Circulation 1976;54:430-5. 18. Iinuma H, Dreifus LS, Mazgalev T, Price R, Michelson
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EL. Role of the perinodal region in atrioventricular nodal reentry: evidence in an isolated rabbit heart preparation. J Am Coli Cardiol 1983;2:465-73. Holman WL, Ikeshita M, Lease JG, Smith PK, Ferguson TB Jr, Cox JL. Elective prolongation of atrioventricular conduction by multiple cryolesions. J THORAC CARDlOVASC SURG 1982;84:554-9. Holman WL, Ikeshita M, Lease JG, Ferguson TB Jr, Lofland GK, Cox JL. Alteration of antegrade atrioventricular conduction by cryoablation of periatrioventricular nodal tissue. J THORAC CARDIOVASC SURG 1984;88:67-75. Holman WL, Ikeshita M, Lease JG, Smith PK, Lofland GK, Cox JL. Cryosurgical modification of retrograde atrioventricular conduction: implications for the surgical treatment of atrioventricular nodal reentry tachycardia. J THORAC CARDIOVASC SURG 1986;91:826-34. Holman WL, Hackel DB, Lease JG, Ikeshita M, Cox JL. Cryosurgical ablation of atrioventricular nodal reentry: histologic localization of the proximal common pathway. Circulation 1988;79:1356-62. Sealy WC, Gallagher JJ, Kasell J. His bundle interruption for control of inappropriate ventricular responses to atrial arrhythmias. Ann Thorac Surg 1981;32:429-38. Scheinman MM, Morady F, Hess DS, Gonzalez R. Catheter induced ablation of the atrioventricular junction to control refractory supraventricular arrhythmias. JAMA 1982;248:851-5. Johnson DC, Nunn GR, Meldrum-Hanna W. Surgery for atrioventricular node reentry tachycardia: the surgical dissection technique. Semin Thorac Cardiovasc Surg 1989;1: 53-7. Johnson DC, Nunn GR, Richards DA, Uther JB, Ross DL. Surgical therapy for supraventricular tachycardia: a potential curable disorder. J THORAC CARDIOVASC SURG 1987;93:913-8. Gartman DM, Bardy GH, Williams AB, Ivey TD. Direct surgical treatment of atrioventricular node reentrant tachycardia. J THORAC CARDIOVASC SURG 1989;98:63-72. Haissaguerre M, Warin JF, Lemetayer P, Sauodi N, Guillem JP, Blanchot P. Closed-chest ablation of retrograde conduction in patients with atrioventricular nodal reentrant tachycardia. N Engl J Moo 1989;320:426-33. Epstein LM, Scheinman MM, Langberg JJ, Chilson D, Goldbery HR, Griffin J'C, Percutaneous catheter modification of the atrioventricular node: a potential cure for atrioventricular node reentrant tachycardia. Circulation 1989; 80:757-68. Roman CA, Wang X, Friday KS, et al. Catheter technique for selectiveablation of slowpathway in AV nodal reentrant tachycardia [Abstract]. PACE 1990;13:498. Wood DL, Hammil SC, Porter CBJ, et al. Cryosurgical modification of atrioventricular conduction for treatment of atrioventricular node reentrant tachycardia. Mayo Clin Proc 1988;63:988-92. Holman WL. Paroxysmal supraventricular tachycardia due to atrioventricular nodal reentry: electrophysiologic
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mechanism and surgical therapy. Cardiac Surg State of Art Rev 1990;4:175-95. 33. Case LL, Crawford FA, Gillette PC, et al. Successful surgery for atrioventricular reentrant tachycardia in a small child. Am Heart J 1989;116:187-9.
Discussion Dr. Miguel Barbero-Marcial (Sao Paulo, Brazil). At the Heart Institute in Sao Paulo, Brazil, since 1987, we have been using a different surgical approach to treat this kind of tachycardia-posterior disconnection of the AV node. Our preliminary results were published in 1988, in Journal ofElectrophysiology. This approach is almost the same as the one that Dr. Sealy proposed for the section of posteroseptal Kent bundles. There is no dissection anterior to the AV node. This procedure is done with cardioplegic arrest. We obtained a 96% success rate in 25 patients. In only one of the 25 patients was the postoperative electrophysiologic study able to induce AV node reentrant tachycardia. There were no complications or deaths. In conclusion, this surgical technique is a nonelectrophysiologically guided approach and therefore the collaboration of the electrophysiologist is not necessary in the operating room. The postoperative AV node conduction remains intact, and this technique demonstrated that a limited and restricted posteroseptal dissection in the same way that Dr. Sealy described it many years ago was enough to obtain success. Dr. Mahomed. Dr. Barbero- Marcial's results reflect those of others who use dissection techniques. Dr. Guiraudon has an initial success rate of 91 %, and long-term follow-up in Dr. Johnson's series reveals a success rate of 83%. Various authors have reported on the cryosurgical technique, and uniformly there has been a 100% success rate with this approach.
The Journal of Thoracic and Cardiovascular Surgery
Dr. James L. Cox (St. Louis, Mo.). The important point to recognize is that there are two types of AV node reentry, one in which the reentrant circuit is located posteriorly in the triangle of Koch (90% to 95%) and the other in which the reentrant circuit is located anteriorly (5% to 10%). The results presented by Dr. Mahomed, in which the surgical dissection had a 20% incidence of heart block, is characteristic of the surgical dissection techniques. The other extreme, in which the reentrant circuit is missed in 4% to 10% of patients, is also quite characteristic, as experienced in Dr. Barbero-Marcial's series. These failures are almost certainly due to the fact that the dissection, which is similar to the surgical dissection technique for AV node reentry, for posteroseptal pathways in the Wolff-Parkinson-White syndrome does not address the anterior type of AV node reentry. Unfortunately, to divide that last 5% to 10% of reentrant circuits that occur anteriorly, additional dissection anteriorly is required, and therein lies the problem of heart block. If you dissect in both areas (anterior and posterior), then you pay the price of a significant level of heart block after the operation. I would like to ask Dr. Mahomed if he could confirm that postoperative heart block in his patients resulted from the anterior portion of the dissection. Dr. Mahomed. That is precisely what happened in both patients. The heart block occurred at the time that we were performing the dissection in the anteroseptal region. I will add one other note regarding the two techniques. The perinodal cryosurgical technique is a straightforward and simple approach to this problem. The dissection technique requires a lot more attention to detail and, for those not familiar with this particular area, a considerable amount of study. I consider the dissection technique a much superior way of approaching refractory AV node reentrant tachycardia.